Chair back frame



FIG. 1 is a front view of a chair back frame showing our new design;

FIG. 2 is a left side view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a top view thereof;

FIG. 6 is a front fractional view of the upper corner of an alternative embodiment, the right upper corner being a mirror image thereof and all other views being the same;

FIG. 7 is a front fractional view of the left upper corner of another alternative embodiment, the right upper corner being a mirror image thereof and all other views being the same; and,

FIG. 8 is a front fractional view of the left upper corner of another alternative embodiment, the right upper corner being a mirror image thereof and all other views being the same. 

The ornamental design for chair back frame, as shown and described. 